THYROID CANCER DIAGNOSIS: Large oral doses of TRH (200 mg per day) were used as a method for evaluating the function of metastic thyroid cancer. TRH had a persistent stimulatory effect on TSH secretion for 14 days. Stimulation of radioiodine uptake in the tumor was more effective with oral TRH than with the customary injection of bovine TSH. Further study is in progress to compare the uptake after TRH with that after endogenous hypothyroidism alone. Medullary thyroid carcinoma contains a high histaminase level. Using the 3H release method of Beaven and Jacobsen, we found that tumor aspirate (3-5 micron 1) had histaminase activity 30 fold higher than normal or in other types of thyroid nodules. The cytology also was diagnostic of medullary carcinoma. Therefore, fine needle aspiration is useful in the diagnosis of this type of thyroid cancer. HYPERTHYROIDISM: Most cases of hyperthyroidism result from a primary defect, or an autoimmune process involving the thyroid gland. We have studied an 18 year old hyperthyroid woman with persistently elevated serum TSH and no evidence or pituitary tumor during 11 years of observation. This patient represents a new syndrome of TSH-induced hyperthyroidism, apparently caused by a selective partial resistance of the pituitary thyrotrophs to the action of thyroid hormone.